【单选题】

For more than 40 years,Earth has been sending out distress signals.At first they were subtle, like the thin shells of bald-eagle eggs that cracked because they were laced (使混合) withDDT. Then the signs were unmistakable, like the covering of smoke over theAmazon rain forest, where farmers and ranchers (牧场主人) set fire to clear lanD、Finally, as the new millennium drew near, it was obvious thatEarth’s pain had become humanity’s pain. The collapse of the NorthAtlantic cod (鳕鱼) fishery put 30,000Canadians out of work and ruined the economies of 700 communities. In 1998, deforestation worsenedChina’s floods, which killed 3,600 people and left 14 million homeless. Population pressures and overcrowding raised the toll from 1999’s rains in LatinAmerica, which killed more than 30,000 people and created armies of environmental refugees.

And how have we responded to four decades of ever louder distress signals We’ve staged a procession, ofEarthDays, formed Green parties, passed environmental laws, forged a few international treaties and organized global gabfests (杂谈会) like the 1992Earth Summit in Rio de Janeiro.All the while, the decline of earth’s ecosystems has continued unabateD、
What will it take for us to get serious about saving our environment When will environmentalism more from being a philosophy promoted by a passionate minority to a way of life that governs mainstream behavior and policy How can we understand thatEarth is one big natural system and that torching tropical rain forests and destroying coral reefs (珊瑚礁) will eventually threaten the well-being of towns and cities everywhere
One crucial step is a true accounting of the state of the planet, a thorough assessment of the health of allEarth’s major ecosystems, from oceans to forests. Only a comprehensive global survey can show how damage to one system is affecting other systems and can determine whetherEarth as a whole is losing its ability to nurture the full diversity of life and the economies of nations.
Our earth can only be effectively saved when ______ .
A、people of all nations become conscious of the danger and make joint efforts.
B．governments in developed countries can formulate more strict laws and regulations.
C．more volunteers can be organized to help the refugees throughout the worlD、
D．the living standards of citizens in developing countries can be greatly raise